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Support single-level multigrid (maxLevels = 1) when extrapolation is disabled #179

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Support single-level multigrid (maxLevels = 1) when extrapolation is disabled #179

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12 changes: 6 additions & 6 deletions include/GMGPolar/igmgpolar.h
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Original file line number Diff line number Diff line change
Expand Up @@ -277,14 +277,14 @@ class IGMGPolar

/* ------------------- */
/* Multigrid Functions */
void multigrid_V_Cycle(int level_depth, Vector<double> solution, Vector<double> rhs, Vector<double> residual);
void multigrid_W_Cycle(int level_depth, Vector<double> solution, Vector<double> rhs, Vector<double> residual);
void multigrid_F_Cycle(int level_depth, Vector<double> solution, Vector<double> rhs, Vector<double> residual);
void extrapolated_multigrid_V_Cycle(int level_depth, Vector<double> solution, Vector<double> rhs,
void multigrid_V_Cycle(int level_depth, Vector<double> solution, ConstVector<double> rhs, Vector<double> residual);
void multigrid_W_Cycle(int level_depth, Vector<double> solution, ConstVector<double> rhs, Vector<double> residual);
void multigrid_F_Cycle(int level_depth, Vector<double> solution, ConstVector<double> rhs, Vector<double> residual);
void extrapolated_multigrid_V_Cycle(int level_depth, Vector<double> solution, ConstVector<double> rhs,
Vector<double> residual);
void extrapolated_multigrid_W_Cycle(int level_depth, Vector<double> solution, Vector<double> rhs,
void extrapolated_multigrid_W_Cycle(int level_depth, Vector<double> solution, ConstVector<double> rhs,
Vector<double> residual);
void extrapolated_multigrid_F_Cycle(int level_depth, Vector<double> solution, Vector<double> rhs,
void extrapolated_multigrid_F_Cycle(int level_depth, Vector<double> solution, ConstVector<double> rhs,
Vector<double> residual);

/* ----------------------- */
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138 changes: 61 additions & 77 deletions include/GMGPolar/setup.h
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Original file line number Diff line number Diff line change
Expand Up @@ -42,24 +42,22 @@ void GMGPolar<DomainGeometry, DensityProfileCoefficients>::setup()
}

if (!is_uniform_refinement) {
throw std::runtime_error(
"Extrapolation Error: Finest PolarGrid does not originate from a single uniform refinement.");
Comment on lines -45 to -46
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@julianlitz julianlitz Feb 17, 2026 •
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Abort immediately may not be a good idea. Better replace by a warning?

std::cerr << "Warning: Finest PolarGrid does not originate from a single uniform refinement.\n";
}
}

// ---------------------------------------------------------- //
// Building PolarGrid and LevelCache for all multigrid levels //
// ---------------------------------------------------------- //
number_of_levels_ = chooseNumberOfLevels(*finest_grid); /* Implementation below */
number_of_levels_ = chooseNumberOfLevels(*finest_grid);
levels_.clear();
levels_.reserve(number_of_levels_);

int level_depth = 0;
auto finest_levelCache = std::make_unique<LevelCache>(*finest_grid, density_profile_coefficients_, domain_geometry_,
cache_density_profile_coefficients_, cache_domain_geometry_);
levels_.emplace_back(level_depth, std::move(finest_grid), std::move(finest_levelCache), extrapolation_, FMG_);
Comment on lines -57 to -60
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@julianlitz julianlitz Feb 17, 2026

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Avoid variable shadowing in later loops.

levels_.emplace_back(0, std::move(finest_grid), std::move(finest_levelCache), extrapolation_, FMG_);

for (level_depth = 1; level_depth < number_of_levels_; level_depth++) {
for (int level_depth = 1; level_depth < number_of_levels_; level_depth++) {
auto current_grid = std::make_unique<PolarGrid>(coarseningGrid(levels_[level_depth - 1].grid()));
auto current_levelCache =
std::make_unique<LevelCache>(*current_grid, density_profile_coefficients_, domain_geometry_,
Expand All @@ -81,84 +79,70 @@ void GMGPolar<DomainGeometry, DensityProfileCoefficients>::setup()
if (verbose_ > 0)
printSettings();

// -------------------------------------------------------
// Initializing various operators based on the level index
// ------------------------------------------------ //
// Define residual operator on all multigrid levels //
// ------------------------------------------------ //
for (int level_depth = 0; level_depth < number_of_levels_; level_depth++) {
// ---------------------- //
// Level 0 (finest Level) //
// ---------------------- //
if (level_depth == 0) {
auto start_setup_smoother = std::chrono::high_resolution_clock::now();
switch (extrapolation_) {
case ExtrapolationType::NONE:
full_grid_smoothing_ = true;
levels_[level_depth].initializeSmoothing(domain_geometry_, density_profile_coefficients_,
DirBC_Interior_, max_omp_threads_,
stencil_distribution_method_);
break;
case ExtrapolationType::IMPLICIT_EXTRAPOLATION:
full_grid_smoothing_ = false;
levels_[level_depth].initializeExtrapolatedSmoothing(domain_geometry_, density_profile_coefficients_,
DirBC_Interior_, max_omp_threads_,
stencil_distribution_method_);
break;
case ExtrapolationType::IMPLICIT_FULL_GRID_SMOOTHING:
full_grid_smoothing_ = true;
levels_[level_depth].initializeSmoothing(domain_geometry_, density_profile_coefficients_,
DirBC_Interior_, max_omp_threads_,
stencil_distribution_method_);
break;
case ExtrapolationType::COMBINED:
full_grid_smoothing_ = true;
levels_[level_depth].initializeSmoothing(domain_geometry_, density_profile_coefficients_,
DirBC_Interior_, max_omp_threads_,
stencil_distribution_method_);
levels_[level_depth].initializeExtrapolatedSmoothing(domain_geometry_, density_profile_coefficients_,
DirBC_Interior_, max_omp_threads_,
stencil_distribution_method_);
break;
default:
full_grid_smoothing_ = false;
levels_[level_depth].initializeSmoothing(domain_geometry_, density_profile_coefficients_,
DirBC_Interior_, max_omp_threads_,
stencil_distribution_method_);
levels_[level_depth].initializeExtrapolatedSmoothing(domain_geometry_, density_profile_coefficients_,
DirBC_Interior_, max_omp_threads_,
stencil_distribution_method_);
break;
}
auto end_setup_smoother = std::chrono::high_resolution_clock::now();
t_setup_smoother_ += std::chrono::duration<double>(end_setup_smoother - start_setup_smoother).count();
levels_[level_depth].initializeResidual(domain_geometry_, density_profile_coefficients_, DirBC_Interior_,
max_omp_threads_, stencil_distribution_method_);
levels_[level_depth].initializeResidual(domain_geometry_, density_profile_coefficients_, DirBC_Interior_,
max_omp_threads_, stencil_distribution_method_);
}
Comment on lines +82 to +88
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@julianlitz julianlitz Feb 17, 2026

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Extract Residual initialization


// ----------------------------------------- //
// Build direct solver on the coarsest level //
// ----------------------------------------- //
auto start_setup_directSolver = std::chrono::high_resolution_clock::now();
levels_[number_of_levels_ - 1].initializeDirectSolver(domain_geometry_, density_profile_coefficients_,
DirBC_Interior_, max_omp_threads_,
stencil_distribution_method_);
auto end_setup_directSolver = std::chrono::high_resolution_clock::now();
t_setup_directSolver_ += std::chrono::duration<double>(end_setup_directSolver - start_setup_directSolver).count();
Comment on lines +90 to +98
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@julianlitz julianlitz Feb 17, 2026

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Extract DirectSolver initialization


// ---------------------------------------------------------- //
// Build the full-grid smoother and the extrapolated smoother //
// ---------------------------------------------------------- //
auto start_setup_smoother = std::chrono::high_resolution_clock::now();

bool do_full_grid_smoothing = false;
bool do_extrapolated_smoothing = false;

switch (extrapolation_) {

case ExtrapolationType::NONE:
do_full_grid_smoothing = true;
break;

case ExtrapolationType::IMPLICIT_EXTRAPOLATION:
do_extrapolated_smoothing = true;
break;

case ExtrapolationType::IMPLICIT_FULL_GRID_SMOOTHING:
do_full_grid_smoothing = true;
break;

case ExtrapolationType::COMBINED:
do_full_grid_smoothing = true;
do_extrapolated_smoothing = true;
break;
}

full_grid_smoothing_ = do_full_grid_smoothing;

if (number_of_levels_ > 1) {
if (do_full_grid_smoothing) {
levels_[0].initializeSmoothing(domain_geometry_, density_profile_coefficients_, DirBC_Interior_,
max_omp_threads_, stencil_distribution_method_);
}
// -------------------------- //
// Level n-1 (coarsest Level) //
// -------------------------- //
else if (level_depth == number_of_levels_ - 1) {
auto start_setup_directSolver = std::chrono::high_resolution_clock::now();
levels_[level_depth].initializeDirectSolver(domain_geometry_, density_profile_coefficients_,
DirBC_Interior_, max_omp_threads_,
stencil_distribution_method_);
auto end_setup_directSolver = std::chrono::high_resolution_clock::now();
t_setup_directSolver_ +=
std::chrono::duration<double>(end_setup_directSolver - start_setup_directSolver).count();
levels_[level_depth].initializeResidual(domain_geometry_, density_profile_coefficients_, DirBC_Interior_,
max_omp_threads_, stencil_distribution_method_);
if (do_extrapolated_smoothing) {
levels_[0].initializeExtrapolatedSmoothing(domain_geometry_, density_profile_coefficients_, DirBC_Interior_,
max_omp_threads_, stencil_distribution_method_);
}
// ------------------- //
// Intermediate levels //
// ------------------- //
else {
auto start_setup_smoother = std::chrono::high_resolution_clock::now();
for (int level_depth = 1; level_depth < number_of_levels_ - 1; level_depth++) {
levels_[level_depth].initializeSmoothing(domain_geometry_, density_profile_coefficients_, DirBC_Interior_,
max_omp_threads_, stencil_distribution_method_);
auto end_setup_smoother = std::chrono::high_resolution_clock::now();
t_setup_smoother_ += std::chrono::duration<double>(end_setup_smoother - start_setup_smoother).count();
levels_[level_depth].initializeResidual(domain_geometry_, density_profile_coefficients_, DirBC_Interior_,
max_omp_threads_, stencil_distribution_method_);
}
}
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@julianlitz julianlitz Feb 17, 2026

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Extract Smoother initialization. Simpler to read.

auto end_setup_smoother = std::chrono::high_resolution_clock::now();
t_setup_smoother_ += std::chrono::duration<double>(end_setup_smoother - start_setup_smoother).count();

auto end_setup = std::chrono::high_resolution_clock::now();
t_setup_total_ = std::chrono::duration<double>(end_setup - start_setup).count();
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12 changes: 9 additions & 3 deletions src/GMGPolar/MultigridMethods/extrapolated_multigrid_F_Cycle.cpp
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
#include "../../../include/GMGPolar/gmgpolar.h"

void IGMGPolar::extrapolated_multigrid_F_Cycle(int level_depth, Vector<double> solution, Vector<double> rhs,
void IGMGPolar::extrapolated_multigrid_F_Cycle(int level_depth, Vector<double> solution, ConstVector<double> rhs,
Vector<double> residual)
{
assert(0 <= level_depth && level_depth < number_of_levels_ - 1);
Expand Down Expand Up @@ -93,8 +93,14 @@ void IGMGPolar::extrapolated_multigrid_F_Cycle(int level_depth, Vector<double> s
assign(next_level.residual(), 0.0);

/* Step 3: Solve for the error by recursively calling the multigrid cycle. */
multigrid_F_Cycle(level_depth + 1, next_level.residual(), next_level.error_correction(), next_level.solution());
multigrid_V_Cycle(level_depth + 1, next_level.residual(), next_level.error_correction(), next_level.solution());
multigrid_F_Cycle(level_depth + 1,
next_level.residual(), // error (solution)
next_level.error_correction(), // coarse residual (rhs)
next_level.solution()); // workspace
multigrid_V_Cycle(level_depth + 1,
next_level.residual(), // error (solution)
next_level.error_correction(), // coarse residual (rhs)
next_level.solution()); // workspace
}

/* Interpolate the correction */
Expand Down
7 changes: 5 additions & 2 deletions src/GMGPolar/MultigridMethods/extrapolated_multigrid_V_Cycle.cpp
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
#include "../../../include/GMGPolar/gmgpolar.h"

void IGMGPolar::extrapolated_multigrid_V_Cycle(int level_depth, Vector<double> solution, Vector<double> rhs,
void IGMGPolar::extrapolated_multigrid_V_Cycle(int level_depth, Vector<double> solution, ConstVector<double> rhs,
Vector<double> residual)
{
assert(0 <= level_depth && level_depth < number_of_levels_ - 1);
Expand Down Expand Up @@ -93,7 +93,10 @@ void IGMGPolar::extrapolated_multigrid_V_Cycle(int level_depth, Vector<double> s
assign(next_level.residual(), 0.0);

/* Step 3: Solve for the error by recursively calling the multigrid cycle. */
multigrid_V_Cycle(level_depth + 1, next_level.residual(), next_level.error_correction(), next_level.solution());
multigrid_V_Cycle(level_depth + 1,
next_level.residual(), // error (solution)
next_level.error_correction(), // coarse residual (rhs)
next_level.solution()); // workspace
}

/* Interpolate the correction */
Expand Down
12 changes: 9 additions & 3 deletions src/GMGPolar/MultigridMethods/extrapolated_multigrid_W_Cycle.cpp
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
#include "../../../include/GMGPolar/gmgpolar.h"

void IGMGPolar::extrapolated_multigrid_W_Cycle(int level_depth, Vector<double> solution, Vector<double> rhs,
void IGMGPolar::extrapolated_multigrid_W_Cycle(int level_depth, Vector<double> solution, ConstVector<double> rhs,
Vector<double> residual)
{
assert(0 <= level_depth && level_depth < number_of_levels_ - 1);
Expand Down Expand Up @@ -93,8 +93,14 @@ void IGMGPolar::extrapolated_multigrid_W_Cycle(int level_depth, Vector<double> s
assign(next_level.residual(), 0.0);

/* Step 3: Solve for the error by recursively calling the multigrid cycle. */
multigrid_W_Cycle(level_depth + 1, next_level.residual(), next_level.error_correction(), next_level.solution());
multigrid_W_Cycle(level_depth + 1, next_level.residual(), next_level.error_correction(), next_level.solution());
multigrid_W_Cycle(level_depth + 1,
next_level.residual(), // error (solution)
next_level.error_correction(), // coarse residual (rhs)
next_level.solution()); // workspace
multigrid_W_Cycle(level_depth + 1,
next_level.residual(), // error (solution)
next_level.error_correction(), // coarse residual (rhs)
next_level.solution()); // workspace
}

/* Interpolate the correction */
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